commit b233920c97a6201eb47fbafd78365c6946e6d7b6
author Alexei Starovoitov <ast@kernel.org> Thu Dec 13 11:42:31 2018 -0800
committer Daniel Borkmann <daniel@iogearbox.net> Sat Dec 15 01:28:32 2018 +0100
tree b12e159f1af740aea1e6ea95a6944e2341689e09
parent eb415c98980fd13618c64b0d88c2439103b4a627

bpf: speed up stacksafe check

Don't check the same stack liveness condition 8 times.
once is enough.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Edward Cree <ecree@solarflare.com>
Acked-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

kernel/bpf/verifier.c

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index ba8e313..0c6deb3 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -5204,9 +5204,11 @@ static bool stacksafe(struct bpf_func_state *old,
 	for (i = 0; i < old->allocated_stack; i++) {
 		spi = i / BPF_REG_SIZE;
 
-		if (!(old->stack[spi].spilled_ptr.live & REG_LIVE_READ))
+		if (!(old->stack[spi].spilled_ptr.live & REG_LIVE_READ)) {
+			i += BPF_REG_SIZE - 1;
 			/* explored state didn't use this */
 			continue;
+		}
 
 		if (old->stack[spi].slot_type[i % BPF_REG_SIZE] == STACK_INVALID)
 			continue;